1. Field of the Invention
The present invention relates to a thin film transistor using an oxide semiconductor film and a display device using the same.
2. Description of the Related Art
In recent years, attention is being paid to a thin film transistor (TFT) using a semiconductor whose main component is an oxide (hereinbelow, called oxide semiconductor) for an active layer. It is known that the electron mobility of the oxide semiconductor is higher than that of amorphous silicon (α-Si) generally used for a liquid crystal display or the like, and the oxide semiconductor has excellent electric characteristics. As such oxide semiconductors, an oxide semiconductor whose main component is zinc oxide (ZnO) (refer to Patent document 1: Japanese Unexamined Patent Application Publication No. 2002-76356), an oxide semiconductor whose main component is In—M—Zn—O (M denotes at least one of gallium (Ga), aluminum (Al), and iron (Fe) (refer to Patent document 2: Japanese Unexamined Patent Application Publication No. 2007-134496), and the like are proposed. In a thin film transistor of the patent document 2, by making a source electrode and a drain electrode formed on the oxide semiconductor, of a metal having a specific work function, a high on/off ratio is realized.